A loader vehicle generally includes a wheeled tractor or other engine-driven vehicle. A bucket is attached to one end by two arms. The arms lift and rotate the bucket under power and control from the tractor. In its lowest position, the bucket may be maintained substantially level with the ground for scraping, digging and dozing dirt, gravel, grain or other material. In its highest position, the bucket is several feet off the ground. Rotation of the bucket allows the bucket to roll back, to prevent spillage of contents during transport and to roll forward for dumping. The vehicle includes a hydraulic system for raising, lowering and rotating the bucket. An operator in a cab controls the operation of the loader. A backhoe-loader vehicle includes a bucket at one end and a backhoe at the other end.
The combination of bucket and arms is known as a boom. The two arms are attached to the vehicle chassis at one end and to the bucket at the other end. The connection to the chassis is known as the upper pivot point. At the upper pivot point, the arms rotate about an axis defined by the points of attachment between the arms and the chassis. Hydraulic cylinders are connected between the arm and chassis. Operation of the hydraulic cylinders rotates the arms about the axis, raising and lowering the boom.
The bucket is also attached to the arms by a rotating connection. The bucket rotates about an axis defined by the points of attachment between the bucket and the arms. A hydraulic linkage controls rotation of the bucket. The hydraulic linkages which move the arms and the bucket are under control of the operator.
Normal use of the boom for loader operation puts extreme mechanical stress on the entire boom assembly. Scraping and lifting operations in particular put both compressive and torsional stress on the boom. The upper pivot points, where the arms attach to the vehicle chassis, are particularly affected by torsional stress.
The forces generated by operation of the loader may be sufficient to structurally damage the loader at the upper pivot points. Damage may occur to one or both of the arms of the boom or to the chassis at the point where the arms attach.
Accordingly, there is a need for a reinforced loader arm assembly capable of withstanding the compressive and torsional stresses associated with operation of the loader.